Mycroft Holmes, Sherlock's younger brother, seems remarkably free of sibling rivalry as he embarks on his third adventure in Fawcett's admirable series. But then why should he suffer from envy? The younger Holmes is clever and successful, has his own eccentric household and even his own Dr. Watson in the earnest and likable person of Paterson Guthrie, his secretary and the novels' narrator. In the treacherous era before the First World War, Sweden's Prince Oscar, ostensibly in London to attend a wedding, has secretly signed a treaty with England. There have been threats against Oscar's life, and when his footman is assassinated near St. Paul's Cathedral, it's clear that the prince is in danger. Mycroft is called upon to protect him. He decides that the safest means to get his charge out of harm's way is via the country's fastest train, the Flying Scotsman. As long as Mycroft can keep his mission a secret, he can get the prince to Edinburgh, where the royal can board a ship to leave the country. With the prince happily disguised as a private citizen, Holmes and Guthrie board the grand train with trepidation. While they wine and dine, they come across old villains and rivals, including the drunken Lord Cameron and the attractive Miss Penelope Gatspy, who brings a light to Guthrie's eyes. Are they innocent passengers or do they have more sinister reasons for being on the train? Fawcett's characters are somewhat less complex than his setting, but they're no less charming. The appealingly grave and perceptive Holmes and the eager Guthrie, mixed into an ingenuous plot that's boosted by Fawcett's effortless descriptions of the era, keep the novel right on track. (Oct.)